hello everyone need some advise i have a 1996 z28 yesterday i was on the way to get my car tuned so i was excited i jumped on the freeway and floored it then i just herd a loud backfire nd the car shutoff tryed starting it cranked but wont start i put a fuel pressure gauge nd it went to 30psi then drops rite away to 0psi i checked for spark nd i have spark just wonderimg if its my fuel pump. I tried to start it today by turning the ignition on and off to build pressure then i tryed to start it and it threw a puff of smoke threw the intake while it was cranking any advise is apreciated thanks... Im jose by the way

 

Can you hear the fuel pump whine?


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Yes its kinda loud

 

Do a search on this site. There should be plenty of info on testing for fuel pressure and pressure drop off.


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30psi on the prime is too low. Should be at least 40psi.

At idle, vacuum hose off the fuel pressure regulator, look for 43.5psi (GM spec is 41-47psi). Reattach the vacuum line and pressure should drop proportional to intake manifold vacuum. A 6 - 8psi from from the "no vacuum" pressure is normal with a stock cam.

If you can get it running, take it out on the road with the pressure gauge taped to the windshield. At WOT, over 5,000rpm should hold at least 40psi.

The rapid drop off will make it hard to start, but if it's the typical problem with the check valve in the fuel pump, it won't affect it once it starts. The drop off could also be caused by a faulty fuel pressure regulator (check for wet fuel in the vacuum line), leaking injectors, or leaking fuel lines, including the short length of hose in the tank that connects the pump to the hard line on the support.

 

ok thanku

 

Hello everyone i replaced my fuel pump nd my car still will not start i checked the pressure and its at 45psi i have very gud spark to it just cranks wont start sumtimes i can hear air coming out the intake/throttlebody any advise thanks

 

Do a compression test.....that backfire might have been something serious........timing chain comes to mind.

 

^^^ agree compression test would take some things out of the equation. when it backfired did it go through the exhaust or from under the hood? rotor could have come lose, valve could be sticking, pushrod could be outa place or bent, timing chain could have jumped. have you been able to scann for any trouble codes?

 

Yea it backfired threw the exhaust and it was pretty loud
i will do a compression test tomorow thanks i tried to scan it but no codes cause my batt went bad had to replace it and the codes cleared thanks again for the advise bw hunter.....craby will post tomorrow

 

Hello guys I was only able to do a compresion test on driver side today
Cly 1 has 180 psi
Cyl 3 has 185 psi
Cyl 5 has 190 psi
Cyl 7 has 160 psi
I will do the other side tomorrow any advise or opinions. Apreciated Thanks guys

 

hello guys i started pulling my lt1 apart got the opti spark removed turned it by hand and i can hear sumthing inside loose and moving around SO IM thinking maybe thats my problem but im still going to open it up nd check my chain nd sprockets since im already there just having trouble removing my harmonic balancer hub off i have a puller nd broke two bolts off da puller any advice apreciated thanks

 

If the rotor in the opti is loose and rattling around there's your problem right there so there's no need to keep going.

You need to make sure the center puller is pushing on the crank and NOT the hub. Depending on the puller the center pusher may not be thin enough.

 

yeah the rotor was broken all up inside the opti thanks RAMAIR95TA
I'm ordering a summit brand cap and rotor kit any know if that would be and ok brand thanks for advise anyone

 

I used one with no problem.